Anodization-assisted grinding apparatus and anodization-assisted grinding method

Abstract

To provide a technique capable of minimizing and simplifying an entire apparatus and facilitating recovery of grinding chips and maintenance.SOLUTION: An anodization-assisted grinding apparatus comprises: pouring means 8 which pours an electrolyte W into a space between at least a cathode 7 and a workpiece 1; a DC power source 9 which generates an anodic oxide film on the surface of the workpiece 1 by making the DC current flow to the workpiece 1 via the electrolyte W between an anode 5 and the cathode 7; and a grinding stone 6 which grinds the anodic oxide film of the workpiece 1. The grinding stone 6 is the non-super abrasive grain grindstone. The electrolyte W is poured onto the workpiece 1 from the anode 5 side or the cathode 7 side.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an anodic oxidation-assisted grinding apparatus and an anodic oxidation-assisted grinding method that apply an anodic oxidation reaction occurring on the surface of a workpiece when a direct current is passed through the workpiece via an electrolytic solution, and grind the surface of the workpiece with a grinding wheel.

Background Art

[0002] Conventionally, there has been an anodic oxidation-assisted grinding apparatus for use in a surface grinding apparatus when grinding a workpiece such as a SiC wafer (Patent Document 1). This anodic oxidation-assisted grinding apparatus includes a container for storing an electrolytic solution. When processing a workpiece, the workpiece is immersed in the electrolytic solution stored in the container, and a direct current is passed between the anode, the cathode, and the workpiece through the electrolytic solution. The surface of the workpiece is ground with a grinding wheel by utilizing the anodic oxidation reaction occurring on the surface of the workpiece.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such an anodic oxidation-assisted grinding apparatus, even when grinding a workpiece such as a SiC wafer, the surface of the SiC wafer becomes soft due to anodic oxidation, so it becomes possible to use a grinding wheel with general abrasive grains such as cerium oxide or free abrasive grains. Compared with the case of grinding with a diamond grinding wheel, the damage to the surface of the SiC wafer is reduced, the surface roughness after processing is improved, and there is an advantage that the tool cost can be reduced due to non-superabrasive grinding wheels.

[0005] However, conventional anodizing-assisted grinding equipment has several drawbacks: the workpiece is immersed in an electrolyte solution stored in a container, making the entire grinding apparatus large and complex; and grinding debris generated by grinding the workpiece with the grinding wheel accumulates in the electrolyte solution in the container, making it difficult to collect the debris and perform maintenance.

[0006] In view of the aforementioned conventional problems, the present invention aims to provide an anodizing-assisted grinding apparatus and an anodizing-assisted grinding method that can miniaturize and simplify the entire apparatus, as well as facilitate the collection of grinding chips and maintenance. [Means for solving the problem]

[0007] The anodic oxidation-assisted grinding apparatus according to the present invention includes means for flowing an electrolyte between the cathode and the workpiece, means for passing a direct current between the anode, the cathode and the workpiece via the electrolyte to generate an anodic oxide film on the surface of the workpiece, and a grinding wheel for grinding the anodic oxide film on the workpiece.

[0008] It is preferable that the electrolyte be flowed from either the anode or the cathode side. It is preferable that the anode applies a positive potential to the workpiece directly or indirectly via the electrolyte. It is preferable that the anode and the cathode oscillate relative to the workpiece.

[0009] The anodic oxidation-assisted grinding method according to the present invention includes the steps of: flowing an electrolyte solution between the cathode and the workpiece; passing a direct current through the electrolyte solution between the anode, the cathode and the workpiece to generate an anodic oxide film on the surface of the workpiece; and grinding the anodic oxide film of the workpiece with a grinding wheel. [Effects of the Invention]

[0010] According to the present invention, the entire apparatus can be made smaller and simpler, and the collection of grinding chips and maintenance can be made easier. [Brief explanation of the drawing]

[0011] [Figure 1] This is a diagram showing the configuration of an anodizing-assisted grinding apparatus, illustrating a first embodiment of the present invention. [Figure 2] (a) is a bottom view of the cathode, and (b) is a cross-sectional view of the cathode. [Figure 3] (a) is a bottom view showing a modified cathode, and (b) is a cross-sectional view thereof. [Figure 4] (a) is a cross-sectional view showing a modified cathode, and (b) is a bottom view thereof. [Figure 5] (a) and (b) are perspective views showing modified cathodes, and (c) is a plan view showing modified cathodes. [Figure 6] This is a diagram showing the configuration of an oscillating type anodic oxidation-assisted grinding apparatus, illustrating a second embodiment of the present invention. [Figure 7] This is a diagram showing the configuration of an anodizing-assisted grinding apparatus, illustrating a third embodiment of the present invention. [Figure 8] (a) is a cross-sectional view of the cathode, and (b) is a cross-sectional view of the bottom of the cathode. [Figure 9] (a) is a cross-sectional view showing a modified cathode, and (b) is a bottom cross-sectional view thereof. [Figure 10] (a) is a cross-sectional view showing a modified cathode, and (b) is a bottom cross-sectional view thereof. [Figure 11] (a) is a cross-sectional view showing a modified cathode, and (b) is a bottom cross-sectional view thereof. [Figure 12] This is a diagram showing the configuration of an anodizing-assisted grinding apparatus, illustrating a fourth embodiment of the present invention. [Figure 13] (a) and (b) are explanatory diagrams of a whetstone. [Figure 14] This is a diagram showing the configuration of an anodizing-assisted grinding apparatus, illustrating a fifth embodiment of the present invention. [Figure 15] This is a diagram showing the configuration of an anodizing-assisted grinding apparatus, illustrating a sixth embodiment of the present invention. [Figure 16] This is a diagram showing the configuration of an anodizing-assisted grinding apparatus, illustrating a seventh embodiment of the present invention. [Figure 17] This is a diagram showing the configuration of an anodizing-assisted grinding apparatus, illustrating the eighth embodiment of the present invention. [Figure 18] It is a configuration diagram of a grinding device using anodic oxidation showing the ninth embodiment of the present invention. [Figure 19] It is a configuration diagram of a grinding device using anodic oxidation showing the tenth embodiment of the present invention.

Best Mode for Carrying Out the Invention

[0012] Hereinafter, each embodiment of the invention will be described in detail based on the drawings. FIGS. 1 and 2 show the first embodiment of a grinding device using anodic oxidation employed in a surface grinding device. As shown in FIG. 1, this grinding device using anodic oxidation includes a workpiece rotating device 2 on which a workpiece 1 is detachably mounted on the upper surface and rotates in the direction of arrow a around a vertical axis 2a, a grindstone shaft 3 that rotates in the direction of arrow b around a vertical axis 3a and can move forward and backward in the vertical direction, a grinding wheel 6 that is detachably mounted on a grindstone shaft flange 4 at the lower end of the grindstone shaft 3 and can grind the workpiece 1 on the workpiece rotating device 2, a cathode 7 disposed with a minute gap S above the workpiece 1 on the workpiece rotating device 2 in the vicinity of the side of the grinding wheel 6, a flowing means 8 for flowing an electrolytic solution W over the workpiece 1, and a DC power source 9 for flowing a DC current from an anode 5 through the workpiece 1 via the electrolytic solution W to the cathode 7.

[0013] The workpiece rotating device 2 is constituted by a rotating table or the like, and has appropriate chuck means (not shown) such as a vacuum chuck on the mounting surface side of the upper surface, and the workpiece 1 is detachably mounted by the chuck means. The workpiece 1 is, for example, a SiC wafer having conductivity, but any other conductive material may be used.

[0014] The grinding wheel 6 constitutes a grinding grindstone (grinding means) for grinding the workpiece 1 and also serves as the anode 5. The grinding wheel 6 is of a cup type or the like, and has a grindstone base material 10 that can be detachably mounted below the grindstone shaft flange 4 and a conductive grindstone 11 fixed to the lower side of the grindstone base material 10. The conductive grindstone 11 is disposed so as to pass through the center of the workpiece 1 within its blade width.

[0015] The grinding wheel shaft 3, grinding wheel shaft flange 4, and grinding wheel base material 10 are made of metal. A positive potential power supply line 12 of a DC power supply 9 is connected to the upper end of the grinding wheel shaft 3 and other suitable locations so as to be slidable relative to it in the direction indicated by arrow b, and the positive potential of the DC power supply 9 is applied from the conductive grinding wheel 11 of the grinding wheel 6 to the workpiece 1.

[0016] The cathode 7 also serves as a means 8 for supplying the electrolyte W and is positioned on the side of the grinding wheel 6, above the workpiece 1, with a predetermined gap, for example, a minute gap S. Specifically, this gap is a minute gap S of 1 mm or less, preferably 500 μm or less. Hereinafter, this gap will be referred to as the minute gap S, but it does not refer to a gap of a specific size. The cathode 7 is made of a conductive material such as metal and is fixed to the lower side of an insulating support member 13, and the negative potential side power supply line 14 of the DC power supply 9 is connected to it, so that a closed circuit is formed between the workpiece 1, the electrolyte W, the DC power supply 9, the anode 5, and the cathode 7.

[0017] Furthermore, a closed circuit consisting of the workpiece 1, electrolyte W, DC power supply 9, anode 5, and cathode 7 is used to apply a DC current to the workpiece 1, thereby generating an anodic oxide film on its surface. The cathode 7 is positioned such that it overlaps with the workpiece 1 in a large area vertically.

[0018] The cathode 7, which also serves as the flowing means 8, has an electrolyte supply passage 15, and the electrolyte W supplied via an electrolyte supply pipe 16 connected to the support member 13 is flowed from the electrolyte supply passage 15 onto the workpiece 1. The flowing means 8 is composed of the electrolyte supply passage 15 and the electrolyte supply pipe 16.

[0019] This flow-through means 8 can be a single-use type in which the electrolyte W applied to the workpiece 1 is discharged without circulation each time grinding is performed, or it can be a circulating type in which the electrolyte W used once for grinding is recovered at an appropriate location such as downstream of the workpiece rotating device 2, purified by filtering or chemical reaction treatment, and then circulated and supplied to the workpiece 1 again. Therefore, "flow-through" in this embodiment includes both the case in which the electrolyte W is applied to the workpiece 1 and then simply discharged, and the case in which the electrolyte W applied to the workpiece 1 is recovered, purified, circulated, and then applied to the workpiece 1 again. This flow-through means 8 performs the process of flowing the electrolyte W onto the workpiece 1.

[0020] The amount of electrolyte W supplied is at least enough to fill the minute gap S between the cathode 7 and the workpiece 1 with the electrolyte W during grinding. During grinding of the workpiece 1 by the grinding wheel 6, it is also possible to directly apply a positive potential through the contact portion where the conductive grinding wheel 11 of the grinding wheel 6 contacts the upper surface of the workpiece 1. Therefore, the amount of electrolyte W between the conductive grinding wheel 11 and the workpiece 1 only needs to be enough to suppress the electrical resistance at the contact portion between them. Thus, it is sufficient for the electrolyte W to accumulate at least between the workpiece 1 and the cathode 7. Furthermore, as the electrolyte W supplied between the conductive grinding wheel 11 and the workpiece 1, it is also possible to use an electrolytic coolant such as water that is supplied for cooling grinding heat and washing away grinding chips.

[0021] The gap between the cathode 7 and the workpiece 1 is set to a minute gap S necessary for the workpiece 1 on the workpiece rotating device 2 to rotate around the vertical axis 2a without contacting the cathode 7. Therefore, the electrolyte W poured over the workpiece 1 accumulates in the minute gap S on the workpiece 1 and flows outwards due to the centrifugal force of the workpiece 1. The electrolyte W is a liquid that can conduct direct current and may be a water-soluble coolant or tap water.

[0022] The cathode 7 is configured in a rectangular or other box shape in plan view, as shown in Figures 2(a)(b) or 3(a)(b). The cathode 7 in Figures 2(a)(b) is box-shaped with a peripheral wall 7a and a bottom wall 7b, and has a storage section 17 on its interior side that communicates with the electrolyte supply line 16, and multiple vertical supply ports 18 that communicate with the storage section 17 are provided vertically and horizontally on the bottom wall 7b side. The electrolyte supply line 15 is composed of the storage section 17 and the supply ports 18, and after receiving the electrolyte W from the electrolyte supply line 16 into the storage section 17, it is discharged from each supply port 18 to the workpiece 1.

[0023] The cathode 7 in Figures 3(a) and 3(b) is also box-shaped, and is provided with an electrolyte supply passage 15 that includes a storage section 17 and a plurality of supply ports 18, the supply ports 18 being formed in the shape of elongated holes. There are, for example, three elongated supply ports 18, two of which are arranged along two adjacent sides on the bottom surface of the rectangular shape in plan view, and one supply port 18 is arranged diagonally between the two supply ports 18 along the two sides.

[0024] The supply ports 18 of the electrolyte supply passage 15 provided in the cathode 7 can be round holes, elongated holes, or other shapes such as square holes or triangular holes. The supply ports 18 should be arranged in a way that efficiently supplies the electrolyte W to the workpiece 1. For example, in the case of the cathode 7 in Figure 2, as many supply ports 18 as possible should be arranged in a direction corresponding to the workpiece 1, and in the case of the cathode 7 in Figure 3, the corner 18a where the supply ports 18 are concentrated should be positioned closer to the center of the workpiece 1. The supply ports 18 should be arranged appropriately while considering their shape, position, and other circumstances. Furthermore, if the electrolyte W can pass through, a porous metal can be used as the flowing means 8.

[0025] During the grinding process of the workpiece 1, the workpiece rotating device 2, with the workpiece 1 mounted on its upper surface, is rotated in the direction indicated by arrow a, and the electrolyte W is poured onto the upper surface of the workpiece 1 from the electrolyte supply passage 15 of the cathode 7 placed on the workpiece 1. The electrolyte W poured onto the upper surface of the workpiece 1 flows toward the upper surface of the workpiece 1, but at this time, it receives centrifugal force from the workpiece 1 rotating in the direction indicated by arrow a, and diffuses in a thin film along the upper surface of the workpiece 1, flowing from the outer periphery of the upper surface of the workpiece 1 toward the outer periphery of the upper surface of the workpiece rotating device 2.

[0026] Next, as the grinding wheel shaft 3, which rotates in the direction of arrow b, is advanced toward the workpiece 1 in the direction of arrow c, the conductive grinding wheel 11 of the grinding wheel 6 comes into contact with the electrolyte W on the workpiece 1. When the conductive grinding wheel 11 and the electrolyte W come into contact, the positive potential of the DC power supply 9 is applied to the workpiece 1 via the grinding wheel shaft 3, the conductive grinding wheel 11, and the electrolyte W, so a DC current flows from the conductive grinding wheel 11, which constitutes the anode 5, through the electrolyte W, the workpiece 1, and the electrolyte W to the cathode 7.

[0027] When the conductive grinding wheel 11 advances further in the direction indicated by arrow c and comes into contact with the workpiece 1, a positive potential is directly applied from the conductive grinding wheel 11 to the workpiece 1, further reducing the electrical resistance between the conductive grinding wheel 11 and the workpiece 1. As a result, the portion of the workpiece 1 facing the cathode 7 becomes anodized, and anodic oxidation occurs as the surface becomes anodized, creating a soft anodic oxide film on the surface of the workpiece 1. This improves the grindability of the upper surface of the workpiece 1, and by cutting with the grinding wheel 6, the anodic oxide film on the surface of the workpiece 1, which has been softened by the anodic oxidation reaction, can be ground away and removed. The anodic oxide film on the surface of the workpiece 1 is formed more efficiently as the minute gap S between the workpiece 1 and the cathode 7 becomes smaller.

[0028] This anodizing-assisted grinding apparatus eliminates the need to immerse the workpiece 1 in an electrolyte solution stored in a container, as was required in conventional methods. This allows for a smaller and simpler overall apparatus compared to conventional methods where a container was essential. Furthermore, since the anodized film is ground and removed by the grinding wheel 6 while the electrolyte solution W is continuously flowing, the grinding debris can be washed away by the flowing electrolyte solution W. Therefore, the grinding debris can be easily collected outside the machine, and the maintenance of the apparatus can be simplified.

[0029] When the grinding wheel 6 cuts into the workpiece 1 in the direction indicated by arrow c, there are several methods for controlling this process, including a constant speed control method that controls the cutting speed to a constant cutting load, a constant load control method that controls the cutting speed to an arbitrary rotational load, and an oxidation rate response method that controls the process according to the anodizing rate of the surface of the workpiece 1. In the case of the constant load control method, the smaller the rotational load, the faster the cutting speed is controlled, and if the rotational load becomes too high, the grinding wheel 6 is controlled to move away from the workpiece 1.

[0030] The electrolyte supply passage 8 of the cathode 7 may be provided with an electrolyte W storage section 17 that opens downward, as shown in Figures 4(a) and 4(b). That is, the cathode 7 may be configured as a downward-opening shape with an upper wall portion 7c and a peripheral wall portion 7a, with the inside serving as the storage section 17, and the electrolyte W supplied from the electrolyte supply pipe 16 may be stored in the storage section 17 while being poured over the workpiece 1 located below the cathode 7.

[0031] The cathode 7, including the electrolyte supply path 15, can be of any shape, not only the circular shape shown in plan view in Figure 5(a) and the fan shape shown in plan view in Figure 5(b).

[0032] For example, as shown in Figure 5(c), the inner peripheral wall portion 7d of the peripheral wall portion 7a surrounding the storage portion 17 may be configured in a substantially arc shape along the outer circumference of the grinding wheel 6, while the outer peripheral wall portion 7e, which is further away from the grinding wheel 6, may be configured in a substantially arc shape along the outer circumference of the workpiece 1. It is desirable to position the inner peripheral wall portion 7d near the grinding wheel 6. The outer peripheral wall portion 7e may be positioned either inside or outside the outer edge of the workpiece 1.

[0033] Figure 6 illustrates a second embodiment of the present invention. This anodizing-assisted grinding apparatus is of the oscillating type, and as shown in Figures 6(a) and 6(b), the grinding wheel 6, cathode 7 and workpiece 1 are configured to oscillate relative to each other in the substantially radial direction of the workpiece 1 (directions indicated by arrows d and e).

[0034] As for the oscillation means, there are two methods: one in which the grinding wheel 6 and cathode 7 are positioned in fixed positions and the workpiece rotating device 2 on which the workpiece 1 is mounted is moved back and forth in the oscillation direction; and another in which the workpiece rotating device 2 on which the workpiece 1 is mounted is positioned in fixed positions and the grinding wheel 6 and cathode 7 are moved back and forth in the oscillation direction. Other configurations are the same as in the first embodiment.

[0035] By performing grinding while the grinding wheel 6, cathode 7, and workpiece 1 oscillate relative to each other in the directions indicated by arrows d and e, oxidation of the upper surface of the workpiece 1 and grinding of the upper surface of the workpiece 1 are efficiently performed.

[0036] In other words, when using a cup-shaped grinding wheel 6, the grinding position is adjusted so that the center of the workpiece 1 passes through the width of the cup-shaped grinding wheel 19. However, because the center of the workpiece 1 is not under the cathode 7, the anodizing efficiency near the center of the workpiece 1 is drastically reduced.

[0037] However, in order to efficiently oxidize the upper surface of the workpiece 1 and grind the upper surface of the workpiece 1, the workpiece rotating device 2 is moved back and forth in the approximately radial direction of the workpiece 1 until the center of the workpiece 1 is below or near the cathode 7, and the oscillating motion of the grinding wheel 6 and the cathode 7 with respect to the workpiece 1 is repeated. This has the advantage that even when using a cup-shaped grinding wheel 19, the amount of overlap between the workpiece 1 and the cathode 7 increases, and the anodic oxidation efficiency of the workpiece 1 is significantly improved.

[0038] If spark-out occurs before the end of the grinding process, the DC power supply 9 is turned off to stop the anodizing of the upper surface of the workpiece 1, and the oscillation operation continues in the same state as normal grinding.

[0039] The typical surface roughness index after normal finish grinding is around 1 nmRa, while the index for surface roughness after CMP (chemical mechanical polishing), a subsequent process after grinding, is 0.1 nmRa. The closer the surface roughness after finish grinding approaches 0.1 nmRa, the less burden is placed on the subsequent CMP process.

[0040] Therefore, by applying this anodizing-assisted grinding apparatus to the SiC wafer processing process, the surface roughness after grinding can be improved, reducing the burden on the CMP process and contributing to a reduction in the total cost of SiC wafer manufacturing.

[0041] Furthermore, the abrasive grains used in this anodizing-assisted grinding apparatus shall be general abrasive grains (including cerium oxide and zirconium oxide). General abrasive grains refer to all abrasive grains except superabrasive grains (diamond and CBN). In addition, since there is no need to use superabrasive grains, tool costs can be reduced.

[0042] Figures 7 and 8 illustrate a third embodiment of the present invention. In this anodizing-assisted grinding apparatus, as shown in Figure 7, an electrolyte supply passage 15 is formed on the outer circumference of a rectangular cathode 7. The cathode 7 is provided below an insulating support member 13, as shown in Figures 8(a) and 8(b). Below the support member 13, an insulating peripheral wall portion 20 is provided at a predetermined interval (for example, several millimeters) surrounding the outer circumference of the cathode 7, and an electrolyte supply passage 15 is formed between the cathode 7 and the peripheral wall portion 20, through which the electrolyte W is poured onto the workpiece 1 from a supply port 18 at the lower end. The cathode 7 and the peripheral wall portion 20 are fixed to the lower side of the support member 13.

[0043] The electrolyte supply passage 15 is arranged in a rectangular shape along the four outer sides of the cathode 7, and an electrolyte supply pipe 16 is connected to the support member 13 side of the electrolyte supply passage 15 on one side. The other configurations are the same as in each embodiment.

[0044] When the electrolyte supply passage 15 is provided on the outer circumference of the cathode 7 in this manner, it is easier to manufacture compared to when a supply port 18 is provided that penetrates vertically through the bottom wall portion 7b of the cathode 7, as shown in Figure 2. Furthermore, since the entire lower surface of the cathode 7 can be made to face the upper surface of the workpiece 1, sufficient overlap between the cathode 7 and the workpiece 1 can be ensured, which has the advantage of increasing the oxidation efficiency of the upper surface of the workpiece 1.

[0045] The electrolyte supply passage 15 outside the cathode 7 can also be configured as shown in Figures 9 to 11. In Figures 9(a) and 9(b), the electrolyte supply passage 15 is formed in a U-shape, spanning three sides of the cathode 7 and the peripheral wall portion 20, and the electrolyte supply pipe 16 is connected to approximately the center of the longitudinal direction of the passage.

[0046] In Figures 10(a) and 10(b), the electrolyte supply passage 15 is formed on one side between the cathode 7 and the peripheral wall 20, and the electrolyte supply pipe 16 is connected to the support member 13 side of the approximately central part of the electrolyte supply passage 15. In Figures 11(a) and 11(b), the electrolyte supply passage 15 is formed on two opposing sides between the cathode 7 and the peripheral wall 20, and the electrolyte supply pipe 16 is connected to the approximately central part of each electrolyte supply passage 15. It is also possible to provide the electrolyte supply passage 15 on two adjacent sides out of the four sides between the cathode 7 and the peripheral wall 20.

[0047] Figure 12 illustrates a fourth embodiment of the present invention. In this anodizing-assisted grinding apparatus, an electrolyte supply passage 15 is provided in the central part spanning the grinding wheel spindle 3 and the grinding wheel 6, and an electrolyte supply pipe 16 is connected to this electrolyte supply passage 15 at the upper end of the grinding wheel spindle 3.

[0048] In this embodiment, the electrolyte W supplied from the electrolyte supply pipeline 16 through the electrolyte supply passage 15 is flowed onto the upper surface of the workpiece 1 from the inner circumference of the conductive grinding wheel 11, which also serves as the anode 5 at the lower end of the grinding wheel shaft 3, using centrifugal force.

[0049] Specifically, the electrolyte W supplied via the electrolyte supply pipeline 16 flows down through the electrolyte supply passage 15 to the lower end of the grinding wheel 6, and then, under the centrifugal force of the grinding wheel 6 rotating in the direction indicated by arrow b, diffuses in a film-like manner along the lower surface 10a of the grinding wheel base material 10, reaching the inner circumference of the conductive grinding wheel 11.

[0050] The electrolyte W that reaches the inner circumference of the conductive grinding wheel 11 flows sequentially downward along the inner circumference of the conductive grinding wheel 11 and is poured onto the upper surface of the workpiece 1. Then, the electrolyte W on the upper surface of the workpiece 1 is affected by the centrifugal force caused by the rotation of the workpiece 1 and flows outwards along the upper surface of the workpiece 1 through the minute gap between the workpiece 1 and the conductive grinding wheel 11. In this way, the electrolyte W can be filled into the gaps between the anode 5 and the workpiece 1, and between the cathode 7 and the workpiece 1.

[0051] If the conductive grinding wheel 11 is configured such that block-shaped segment grinding wheels 11a are arranged in a ring with predetermined gaps 11b in the circumferential direction, as shown in Figure 13(a), or that radial flow passages 11d are provided at predetermined intervals in the circumferential direction, as shown in Figure 13(b), the electrolyte W will flow outwards through the gaps 11b and flow passages 11d, thus allowing the electrolyte W to be easily diffused.

[0052] In this manner, an electrolyte W pouring means 8 is provided on the anode 5 side, allowing the electrolyte W to be poured onto the workpiece 1 from the anode 5 side. Furthermore, since the pouring means 8 does not limit the size of the cathode 7, the size of the cathode 7 can be sufficiently secured according to the area of ​​the placement location of the cathode 7, and the amount of overlap between the cathode 7 and the workpiece 1 can be increased, thereby improving the efficiency of the anodic oxidation reaction.

[0053] Figure 14 illustrates a fifth embodiment of the present invention. In this anodic oxidation-assisted grinding apparatus, the pouring port 16a at the tip of the electrolyte supply pipe 16, which constitutes the pouring means 8, is positioned facing downwards at a suitable location such as between the grinding wheel 6 and the cathode 7, or near their sides, and the electrolyte W is poured downwards from the pouring port 16a onto the workpiece 1. The other configurations are the same as in each embodiment.

[0054] If it is possible to pour the electrolyte W onto the workpiece 1 in this manner, the pouring port 16a of the pouring means 8 can also be placed in a location other than the grinding wheel 6 and the cathode 7.

[0055] Figure 15 illustrates a sixth embodiment of the present invention. In this anodizing-assisted grinding apparatus, the pouring port 16a at the tip of the electrolyte supply pipeline 16 constituting the pouring means 8 is positioned diagonally upward or upward toward the lower surface 10a of the grinding wheel base material 10 of the grinding wheel 6, and the electrolyte W is sprayed from the pouring port 16a diagonally upward or upward toward the lower surface 10a of the grinding wheel base material 10.

[0056] In this way, it is possible to use the centrifugal force of the rotating grinding wheel base material 10 to pour the conductive grinding wheel 11 over the workpiece 1 via its inner circumference. Therefore, the pouring means 8 may pour over the workpiece 1 from above, from below upwards, or from the side.

[0057] Figure 16 illustrates a seventh embodiment of the present invention. This anodizing-assisted grinding apparatus grinds a workpiece 1 using a general abrasive grinding wheel 6A (or a grinding pad containing general abrasive grains) equipped with a non-conductive grinding wheel 11C.

[0058] In the case of a general abrasive grinding wheel 6A comprising a conductive grinding wheel base material 10 and a non-conductive grinding wheel 11C mounted below the grinding wheel base material 10, the grinding wheel base material 10 can constitute the anode 5. In this case, the electrolyte W not only fills the space between the workpiece 1 and the cathode 7, but the liquid level H of the electrolyte W on the workpiece 1 is set to the height of the grinding wheel base material 10 so that the electrolyte W comes into contact with the grinding wheel base material 10. As a result, when the grinding wheel base material 10 comes into contact with the electrolyte W, a direct current can be passed from the grinding wheel base material 10 through the electrolyte W, the workpiece 1, and the electrolyte W to the cathode 7.

[0059] In this case as well, the direct current flowing through the workpiece 1 via the electrolyte W causes the surface of the portion of the workpiece 1 that overlaps with the cathode 7 to become anode, and an anodic oxide film is formed on the surface of the workpiece 1. This anodic oxide film can then be removed using a non-conductive grinding wheel 11C with general abrasive grains.

[0060] Therefore, even in the case of a general abrasive grinding wheel 6A using a non-conductive grinding wheel 11C, it is possible to connect the positive potential side power supply line 12 of the DC power supply 9 to the upper end side of the grinding wheel shaft 3 and supply power via the grinding wheel base material 10 without going through the non-conductive grinding wheel 11C.

[0061] In this case, it is necessary to ensure that the DC current flows from the grinding wheel base material 10 through the electrolyte W, the workpiece 1, and the electrolyte W to the cathode 7, so that the anode 5 and cathode 7 do not short-circuit. Factors such as the positional relationship between the anode 5 and cathode 7, the distance (gap) between the cathode 7 and the workpiece 1, and the flow direction of the electrolyte W can be considered, and it is conceivable to prevent a short circuit by appropriately combining any or more of these factors. For example, if the gap between the cathode 7 and the workpiece 1 is small, less than 500 μm, a short circuit between the anode 5 and cathode 7 can be prevented by making the distance between the anode 5 and cathode 7 sufficiently greater than that.

[0062] Furthermore, in order to anode the portion of the workpiece 1 corresponding to the cathode 7, it is necessary to keep the electrical resistance including the electrolyte W from the grinding wheel base material 10 to the workpiece 1 smaller than the electrical resistance including the electrolyte W from the cathode 7 to the workpiece 1.

[0063] Figure 17 illustrates an eighth embodiment of the present invention. In this anodizing-assisted grinding apparatus, an insulating material 22 is interposed between the grinding wheel shaft flange 4 at the lower end of the grinding wheel shaft 3 and the grinding wheel base material 10, and the positive potential side power supply line 12 of the DC power supply 9 is connected to the grinding wheel base material 10 so as to be slidable relative to it.

[0064] In other words, in this embodiment as well, a general abrasive grinding wheel 6A is employed, which has a non-conductive grinding wheel 11C on the lower side of a conductive grinding wheel base material 10. An insulating material 22 is interposed between the grinding wheel shaft flange 4 at the lower end of the grinding wheel shaft 3 and the grinding wheel base material 10, and the positive potential side power supply line 12 of the DC power supply 9 is connected to the grinding wheel base material 10 side so as to be slidable relative to it. The other configurations are the same as in the seventh embodiment.

[0065] By interposing an insulating material 22 between the grinding wheel shaft flange 4 and the grinding wheel base material 10, and connecting the positive potential feed line 12 of the DC power supply 9 to the grinding wheel base material 10, it is possible to apply the positive potential of the DC power supply 9 to the workpiece 1 via the electrolyte W from the grinding wheel base material 10 without going through the grinding wheel shaft 3. Note that insulation between the grinding wheel shaft 3 and the grinding wheel base material 10 may be performed at other locations.

[0066] Figure 18 illustrates a ninth embodiment of the present invention. This anodizing-assisted grinding apparatus is equipped with a separate anode 5 for power supply, in addition to the grinding wheel 6, and a positive potential from a DC power supply 9 is applied to this anode 5. An insulating material 22 is interposed between the grinding wheel flange 4 of the grinding wheel shaft 3 and the conductive grinding wheel base material 10 of the grinding wheel 6. The means for supplying the electrolyte W 8 and other configurations are the same as in each embodiment.

[0067] When a dedicated anode 5 is provided in this manner, the power supply system on the positive potential side can be simplified compared to when a power supply system is provided for the rotating grinding wheel shaft 3 and the grinding wheel base material 10 of the grinding wheel 6. Alternatively, a flow-through means 8 may be provided for the power supply anode 5, and the electrolyte W may be supplied from the anode 5 side to the workpiece 1.

[0068] Figure 19 illustrates a tenth embodiment of the present invention. This anodic oxidation-assisted grinding apparatus integrates the anode 5 and cathode 7, which are dedicated to power supply, by providing them on an insulating support member 23. An insulating portion 23a is provided between the anode 5 and cathode 7 in the support member 23. The means for supplying the electrolyte W 8 and other configurations are the same as in each embodiment.

[0069] With this configuration, the anode 5 and cathode 7 can be treated as a single unit. Compared to the case where the anode 5 and cathode 7 are arranged separately, adjusting the gap between the workpiece 1 and each electrode, as well as attaching and detaching them, is easier, and the area around the electrodes can be miniaturized and arranged efficiently.

[0070] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these embodiments, and various modifications are possible without departing from the spirit of the invention. In each embodiment, an anodizing-assisted grinding apparatus in which the grinding wheel 6 and the workpiece rotating device 2 rotate around a vertical axis is illustrated, but the grinding wheel 6 and the workpiece rotating device 2 may rotate around a horizontal axis or an inclined axis, and the direction of rotation is not a problem.

[0071] The anode 5 is preferably provided on the grinding wheel 6, 6A side, but it may also be provided separately from the grinding wheel 6, 6A. Furthermore, when the anode 5 is in contact with the workpiece 1, the portion of the workpiece 1's surface facing the cathode 7 can be easily anodized. However, even when the anode 5 does not directly contact the workpiece 1 but is electrically connected to it via the electrolyte W, the workpiece 1 can still be anodized in the same way. Therefore, a predetermined gap is required between the cathode 7 and the workpiece 1, but there may or may not be a gap between the anode 5 and the workpiece 1. The anodization reaction of the portion of the workpiece 1's surface facing the cathode 7 is greatly influenced by the size of the gap between the workpiece 1 and the cathode 7, and efficiency tends to improve as the gap becomes smaller. Therefore, it is desirable that the gap between the workpiece 1 and the cathode 7 be minute.

[0072] When the electrolyte W is poured onto the workpiece 1 on the workpiece rotating device 2 by the pouring means 8, it is desirable to set the pouring position of the electrolyte W near the center of the workpiece 1 in order to diffuse the electrolyte W on the workpiece 1 by utilizing the centrifugal force when the workpiece 1 rotates. However, if the gap between the workpiece 1 and the cathode 7 is small, it is possible to penetrate the electrolyte W into the gap between the workpiece 1 and the cathode 7 due to the surface tension of the electrolyte W, etc. Therefore, in this case, even if the pouring position of the electrolyte W is far from the center, the electrolyte W can penetrate between the workpiece 1 and the cathode 7 against the centrifugal force when the workpiece 1 rotates.

[0073] The electrolyte W supplying means 8 may be provided on the cathode 7 side or the anode 5 side, or it may be provided separately from the anode 5 and cathode 7. The planar shape of electrodes such as the cathode 7 with an electrolyte supply function can be appropriately determined considering the conditions around the electrode's placement position, and any external shape can be adopted. In that case, it is desirable to increase the amount of overlap of the cathode 7 with respect to the workpiece 1. [Explanation of Symbols]

[0074] 1 Workpiece 2 Workpiece rotation device 3. Grinding wheel shaft 5 Anode 6. Grinding Wheel 6A General Abrasive Grinding Wheel 7 Cathode W Electrolyte 8. Continuous flow method 9 DC power supply 10 Grinding wheel base material 11 Conductive grinding wheel 11C Non-conductive grinding wheel S micro gap 15 Electrolyte supply path 16 Electrolyte supply line 17 Storage section 18 supply ports 19 Cup-shaped whetstones 20 Peripheral wall

Claims

1. a means for flowing an electrolyte between at least the cathode and the workpiece; a means for passing a direct current between the anode, the cathode, and the workpiece via the electrolytic solution to form an anodic oxide film on the surface of the workpiece; and a grinding wheel for grinding the anodized coating of the workpiece. An anodizing-assisted grinding device characterized by:

2. The electrolyte is poured from the anode side or the cathode side.

2. The anodizing-assisted grinding device according to claim 1.

3. The anode applies a positive potential to the workpiece directly or indirectly via the electrolyte.

3. The anodizing-assisted grinding device according to claim 1 or 2.

4. The anode and the cathode are oscillated relative to the workpiece.

3. The anodizing-assisted grinding device according to claim 1 or 2.

5. a step of flowing an electrolyte between at least the cathode and the workpiece; a step of passing a direct current between the anode, the cathode, and the workpiece via the electrolytic solution to form an anodized film on the surface of the workpiece; and grinding the anodized film of the workpiece with a grinding wheel. An anodizing-assisted grinding method characterized by:

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